Large concrete structures are being built for the production, storage and transportation of oil. The effects of crude oil on the properties of concrete are not well known and little data is available in the published literature. The present investigation is divided into three parts: 1) A study of the mechanical properties of oil saturated hardened cement paste, mortar and concrete. 2) A study of the effect of absorbed oil on the average bond stress, and the bond stress distribution between reinforcing bar and concrete. 3) A study of the changes in the dynamic modulus and logarithmic decrement of concrete soaked in oil for different periods. All the specimens were oven dried to increase the permeability of concrete to oil and to increase the degree of oil saturation. The results were compared with those of similar specimens soaked in water or sealed in polythene bags as control specimens. The mechanical properties. of HCPs, mortar, and concrete studied here were adversely affected by oil saturation. The compressive strength and elastic modulus were reduced by amounts depending on the amount of oil absorbed. The tensile strength was also reduced due to soaking in oil but the reduction was less than that of the companion specimens sealed as a reference. It appears that the oil mainly affects the aggregate-cement bond strength. - i - The average bond strength between steel and concrete, for both plain and deformed bars, decreases with an increase in the amount of absorbed oil. The reduction. for the plain bar was between 1.8-2.3 times greater than that for the deformed bar. The study of the bond stress distribution showed that at the maximum applied-load, the local bond stress at the embedded end of the oil saturated specimens was about six times greater than that at the loaded end. The dynamic modulus of elasticity increased by 12-14% after soaking the concrete in oil for 580 days compared to the oven dried specimens. The increase w~s about 37% less than that of similar water soaked specimens. The studies of logarithmic decrement indicate that the loss of moisture is the most important factor influencing damping capacity.

This thesis presents a detailed investigation on the engineering properties and microstructural characteristics of concrete containing a high volume of fly ash (HVF A). The purpose of the project is to evaluate the concept of using relatively large volumes of fly ash in normal portland cement concrete, and hence enhance the beneficial use of fly ash in value-added products and construction. A total of eight concrete mixtures with and without fly ash was investigated. The proportion of fly ash in all the HVF A concrete mixtures varied from 50 to 80 % by weight of the cementitious materials, with a constant water-to-cementitious ratio of 0.40 for all the mixtures. A high degree of workability was maintained by the use of a superplasticizer. To optimize the pozzolanic activity in the HVF A concrete, silica fume was used in some of the mixes. The total cementitious materials content was kept constant at 350 kg/m3 and 450 kg/m3 respectively. The influence of the different replacement materials and two curing regimes was studied. The study consisted of two parts. The first part is an extensive study of the engineering properties such as strength development, modulus of elasticity, ultrasonic pulse velocity, swelling, and drying shrinkage at various ages up to 18 months. The depth of carbonation of HVF A concrete under different curing regimes was also investigated. A study of the microstructure of HVF A concretes forms the second part of the investigation. Pore structure, air permeability and water absorption of HVF A concretes with different replacement mixtures were studied. A detailed discussion dealing with the change of the morphological phase under different curing regimes is also presented. The results show that HVF A concretes exhibit excellent mechanical properties with good long-term strength development. Compressive strength in the range of 40 to 60 MPa "as achieved for all the HVF A concretes at the age of 90 days. The dynamic modulus of elasticity reached values of the order of 55 GPa at 90 days. Under similar conditions, concretes made with both fly ash and silica fume had engineering properties which were as good as those made with cement replaced by fly ash alone. The use of fly ash to replace both cement and sand has the advantage of mobilizing and combining the benefits and effects of both separate replacements. The HVF A concretes also have low permeability and exhibit good potential characteristics to resist water penetration. Reduction in the volume of large pores was observed with the progress of the pozzolanic reaction. Higher HVF A concrete strength was generally associated with a lower volume of large pores in the concrete. A decrease in the levels of calcium hydroxide was seen with progressive water curing and age in all the HVF A concretes, providing evidence of continued pozzolanic reactivity of the fly ashes. Various empirical relationships and design equations are presented and conclusions are drawn at the end of each part. It is recommended that further research is required to determine the influence on HVF A concretes of extreme curing conditions such as high or low temperature and low moisture availability, and to improve the early strength properties of the HVF A concretes.

No description available.

The demand for road making materials continues to pressurise the supply of traditional good quality aggregates. Over the years, therefore, consideration has been given to alternative materials including industrial wastes. This thesis is concerned with potential use of Minestone, the by-product of coal mining, for the lower structural layers of pavement construction. Because of their clay like nature, Minestones do not merit consideration for such applications in an unbound state and, therefore, some form of stabilisation is necessary. Previous research has demonstrated that certain cement bound minestones, containing between 5 and 10 per cent cement, satisfy current Department of Transport requirements for use in pavement construction and, furthermore, they are not frost susceptible. However, doubts concerning the durability of cement bound minestones still remain. The thesis includes a review of both the cement and lime stabilisation techniques and also traces the origin and development of the methods used to assess the quality and durability of stabilised materials. An experimental study is described in which cement bound minestone specimens were subjected to a programme of tests which examined compressive strength, resistance to immersion, and resistance to freezing and thawing. The results of the tests were related to the properties of the raw materials. It was discovered that the response to cement stabilisation was governed mainly by the source of the minestone and, to a lesser degree, the cement content. It was also found that resistance in the durability tests was generally improved when the initial moisture content was raised above the optimum value. The result suggest that current methods for assessing cement stabilised materials are not appropriate to cement bound minestones. Alternative methods and criteria, based on volume change and retained strength following immersion and freeze-thaw tests, have been proposed. It is believed that these methods and criteria should also apply to other cement bound materials.

The mechanical properties and wear behaviour of B(SiC) fibre-reinforced metal matrix composites (MMCs) and aluminium alloy (2014) produced by metal infiltration technique were determined. Tensile tests were peliormed at different conditions on both the alloy matrix and its composite, and the tensile fracture surfaces were also examined by Scanning Electron Microscopy (SEM). Dry wear of the composite materials sliding on hardened steel was studied using a pin-on-disc type machine. The effect of fibre orientation on wear rate was studied to provide wear resistance engineering data on the MMCs. Tests were carried out with the wear surface sliding direction set normal, parallel and anti-parallel to the fibre axis. Experiments were perfonned for sliding speeds of 0.6, 1.0 and 1.6 m/s for a load range from 12 N to 60 N. A number of sensitive techniques were used to examine worn surface and debris, i.e: Scanning Electron Microscopy (SEM), Backscattered Electron Microscopy (BSEM) and X-ray Photoelectron Spectroscopy (XPS). Finally, the effect of fibre orientation on the wear rate of the Borsic-reinforced plastic matrix composites (PMCs) produced by hot pressing technique was also investigated under identical test conditions. It was found that the composite had a markedly increased tensile strength compared with the matrix. The wear results also showed that the composite exhibited extremely low wear rates compared to the matrix material and the wear rate increased with increasing sliding speed and normal load. The effect of fibre orientation was marked, the lowest wear rates were obtained by arranging the fibre perpendicular to the sliding surface, while the highest wear was obtained for the parallel orientation. The coefficient of friction was found to be lowest in the parallel orientation than the others. Wear of PMCs were influenced to the greatest extent by these test parameters although similar findings were obtained for both composites. Based on the results of analyses using SEM, BSED and XPS, possible wear mechanisms are suggested to explain the wear of these materials.

In Part I of the thesis the effect oif sulphonated melamine formaldehyde (SMF) superplasticizer on the hydration, microstructure and internal chemistry of ordinary Portland cement, as well as on individual pure cement clinker components such as tricalcium aluminate (C3A) was investigated. Conduction calorimetry, thermal analysis, X-ray diffractometry, scanning electron microscopy and pore fluid extraction techniques were used. In order to determine SMF content of the cement pore fluids, it was necessary to develop a new analytical method for SMF. Because of high pH of cement pore fluids the conventional U.V. method was found to be inapplicable. Therefore a new method based on spectrofluorometry was developed; it can be used up to a. pH of about 10, and neutralization can be made using HN03 solution. The role of SMF during cement hydration was further assessed using the method. The results showed that C3A phase of Portland cement adsorbed large amounts of SMF superplasticizers from the aqueous phase of C3A-gypsum mixes in the first few minutes of hydration. In Part II of the thesis, chemical interactions between alkali-resistant (AR) glass fibres and cement matrices was studied. The effect of silica fume additions on the interactions were also investigated. The results of the present work suggest that there are a number of points to be clarified, concerning the use of superplasticizers and AR-glass fibres in cement. The future work to be carried out on superplasticizers may be divided into several groups such as alkali-silica reaction, corrosion of reinforcing steel and durability aspects. Superplasticizers are normally employed as sodium salts. It is evident that addition of superplasticizers into ordinary Portland cement increases the Na+ content of pore solution as well as its pH. Therefore, the rate of alkali-silica reaction may be enhanced due to the increasing pH of cement matrices. Superplasticizers are currently used for the placement of concrete in heavily steel-reinforced structures. The alkaline nature of concrete matrices provides excellent protection for steel reinforcement. However, carbonation of the concrete lowers the pH of the matrix. On the other hand, penetration of aggressive species such as Cl- ions from the sea or other sources accelerates the corrosion of steel reinforcement. There is as yet no detailed study on the chemical behaviour of superplasticizers in chloride- bearing concretes, especially, in relation to their effect on steel reinforcement corrosion kinetics. Superplasticizers greatly influence the morphology of cement hydration products, mainly calcium hydroxide. There is controversy as to whether calcium hydroxide crystals formed in cement paste make a positive or negative contribution to the strength development of cement pastes. In addition, the effect of the presence of thin calcium hydroxide crystals on the durability and long-term properties of cement pastes is not yet known. Zr02-containing commercial AR-glass fibres show poor durability characteristics in a Portland cement matrix, cured in a humid environment, although the deterioration of zirconia glass is much slower than that of ordinary glass. Attack on the fibres is attributed to both the high alkalinity of Portland cement matrices and the growth of hydration products, mainly calcium hydroxide. One solution to these problems seems to be to reduce both the alkalinity and the calcium hydroxide content of cement pastes. Pozzolanic materials such as silica fume, fly ash, slag etc. are very effective in reducing both the pH and the calcium hydroxide content of cement pastes. From the results presented in this thesis, the highly brittle nature of cement pastes with silica fume leads to a decrease in flexural strengths of AR-GFRC composites, although it improves the durability of composites to some extent. The use of other pozzolans, for example, fly ash and slag have not received much attention. Another possibility is the use of less alkaline cement matrices to decrease the chemical attack on AR-glass fibres. In addition to changing composition of cement matrices, the covering of the surface of original glass fibres by alkali- resistant organic or inorganic materials may protect the glass from chemical attack and slow down the corrosion process. Investigations on more alkali-resistant glass compositions may,- also result in the manufacturing of new types of glass fibres.

No description available.

Research work on metal matrix-fibre composites has concentrated in the past on aligned fibre composites. The poor transverse strength of these composites is seen as a major hindrance to their practical use in the majority of engineering applications because stresses exist in more than one direction. Materials with isotropic properties are preferred and consequently reinforcement of composites in three dimensions will be necessary. With this objective, an investigation was conducted to assess the method of fabrication and properties of A1-a110y reinforced with short fibres (SiC and A1 203) randomly oriented in three dimensions. Two composite systems were examined: Al-4.S Cu alloy reinforced with SiC fibre; and Al-3.7S Mg alloy reinforced with A1 203 fibre. The general approach was to establish a satisfactory manufacturing method for the composites before evaluating their mechanical properties. The vortex technique was used to introduce the fibres into the molten alloy. Pre-treatment of the fibres, to induce wetting, and the use of a specially designed device for fibre separation and introduction to the molten A1-ai10ys was found to be necessary so that a uniform distribution of fibres oriented in three dimensions could be achieved. The composites were squeeze cast, under conditions which were experimentally determined, to ensure the production of pore-free castings with fine equiaxed structures. The improvement in tensile strength and ductility of the cast metal, provided by squeeze casting, would be beneficial to composite properties. Composite castings, with up to 10% volume fibre, were produced with a sound structure and with fibres that were uniformly distributed and randomly oriented in three dimensions. It was found that the reaction between the fibres and the respective molten alloy must be closely controlled so that fibre reinforcement can be realised. In this respect the optimum time of contact between the fibres and the molten alloy was experimentally defined for both composite systems. The tensile properties (UTS, 0.1% proof stress, and ductility) of the fibre-free alloys were substantially improved by squeeze casting. The addition of fibre produced further substantial improvement in the tensile properties of the squeeze cast composites, in particular elastic modulus and 0.1% proof stress. Furthermore, composite properties were isotropic. The improvement in the tensile properties of composite castings (as a result of the addition of fibre) was maintained at elevated temperatures. At 250oC, castings of both composite systems with 10% (volume) fibre had 0.1% proof stress and elastic modulus values similar to those for the fibre-free castings at room temperature. The tensile properties of the composite castings were not affected by thermal cycling (at experimental conditions). The fatigue life of the squeeze cast composite was substantially improved over and above the initial improvement in fatigue life of the fibre-free castings produced by squeeze casting. Wear of cutting tools was adversely affected by the presence of fibres.

The micromechanics of reinforcement of model carbon fibre/epoxy composites has been investigated using the technique of Remote Laser Raman Microscopy. The technique allows in situ axial stress monitoring in highly crystalline fibres, such as carbon. For this purpose a remote fibre -optic probe was designed and tested. Tailor - made optics have been introduced at both input and output positions of each fibre - optic to provide laser collimation and maximum efficiency. The probe design takes advantage of the pinhole nature of the optical fibre to achieve depth discrimination. A full characterisation of the high modulusM 40 fibres using conventional testing and Raman Spectroscopy preceded the study of the stress transfer. The study was performed as a function of fibre sizing, coupon geometry and elevated temperature. Model composites were subjected to incremental tensile loading, while the stress in the fibre was monitored at each level of applied strain. The stress transfer regime was studied in the elastic domain using the short fibre coupon test and shear lag approach was employed to model the stress transfer efficiency of the interface through the use of the shear-lag parameter/ The study of the long fibre coupon test led to the identification of interfacial failure mechanisms which were also investigated by Scanning Electron Microscopy (SEM). Finally, the stress build-up in the fibre in the presence of energy dissipation mechanisms was modelled,and the stress-transfer efficiency was assessed at different levels of applied composite strain.

A method of fabrication of a novel cellular composite structure has been devised based on a convoluted sheet of resin-impregnated fabric. The flexural properties of this structure with and without facings have been assessed in four point bending. In flexure the load deflection trace is linear up to a point at which a critical load is reached and the structure fails by a gradual buckling mechanism. The second moment of area of the structure's cross-section has been approximated to that of a square packed array of composite cylinders of equivalent dimensions and this successfully predicts beam properties. The effects of span and tube element geometry on flexural properties were studied to establish a method of predicting the mechanical response of a cellular composite beam in flexure. A failure criterion for the buckling of individual composite cylinders was applied to the cellular composite structure enabling a series of load versus deflection design curves to be drawn for any beam with any geometrical cross-section in any bending configuration. Future commercial prospects for the cellular structure have been anticipated by filing patent applications worldwide. Mechanical tests have been undertaken to establish the originality of the cellular material. The energy absorption capacity of the cellular composite structure was assessed. It was shown that the structure has an unusually high specific energy absorption capacity in comparison to single composite cylinders of equivalent geometric ratios. It was also demonstrated that the energy absorption, which is rate independent, is dependent on cell geometry and the orientation of the reinforcing fabric.